Ultrasonic level sensors monitor and detect liquid levels in containers by using ultrasonic signals. Such ultrasonic level sensors measure the time that it takes for the ultrasonic signal to travel from the transducer to a liquid surface and back to the sensor and then determine the level of the fluid based on the known speed of sound and time. That is, the ultrasonic waves are reflected from the surface of the liquid and the time for the reflected (echo) ultrasonic waves detected back at the transducer is determined. Since the speed of the ultrasonic wave is known, the measured travel time of the wave provides a measure of the distance to the surface of the liquid. Knowing the geometry (e.g., height of the tank and the position the sensor is mounted), an indication of liquid level can then be determined by a controller (e.g., a processor or computer) coupled to or within the transducer. Typical ultrasonic transducers, such as piezoelectric transducers, generate sound waves, at frequencies greater than about 20 kHz which is above the threshold for human hearing.
Some conventional transducers include several mirrors, however, these mirrored transducers suffer from two main factors. First, the mirror is not flat which distorts the length of travel of the ultrasonic signal and second, the structure creates an undesirable surface where the ultrasonic signal is reflected and therefore causing false echoes